Presentation for El Paso County IT on the concepts of Object-Relational Mapping and Dependency injection with a particular focus on the Microsoft Unity DI Container and the Microsoft Entity Framework. Delivered on October 2, 2012.

1. Object-Relational Mapping and Dependency Injection

2. Object-Relational Mapping
ORM Concepts

3. What is ORM?
• Object Relational Mapping is a technique for converting between
incompatible type systems in Object Oriented (OO) programming.
• Primary use is to map between business objects in the application layer and
a relational database.
• Also can be used to map from business object models to data transfer
objects (DTO) or a view model.

4. ORM Advantages and Disadvantages
• Compared to traditional techniques of exchange between an object-oriented
language and a relational database, ORM often reduces the amount of code
that needs to be written.
• Compared to traditional techniques, ORM greatly improves the speed of
application development.
• ORM tools add complexity in areas where proprietary, or database-specific
techniques have been highly optimized.
• Most ORM tools do not perform well during bulk deletions of data or joins.
• Stored procedures may have better performance, but are not portable.
• Object-relational impedance mismatch can result if the business object
model does not closely match the relational data structure.

5. .NET ORM Tools
• Entity Framework: http://msdn.microsoft.com/data/ef
• Telerik OpenAccess: http://www.telerik.com/products/orm.aspx
• Castle Project: http://www.castleproject.org/
• AutoMapper: https://github.com/AutoMapper/AutoMapper

6. Microsoft Entity Framework
Why EF?

7. What is the Entity Framework (EF)?
• EF is Microsoft’s recommended data access technology for new
applications.
• EF is an object-relational mapper that enables .NET developers to work with
relational data using domain-specific objects.
• Supported Databases
• SQL Server
• MySQL
• Oracle
• Sybase
• Any other database that provides an ADO.NET data provider

8. EF Use Patterns
• Database First
• Model First
• Code First
• Code First Migrations

9. Inversion of Control and Dependency Injection

10. What is Inversion of Control (IoC)?
• IoC is an object-oriented programming practice where the object coupling is
bound at run time by an assembler object and is typically not known at
compile time using static analysis.
• Inversion of control as a design guideline serves the following purposes:
• There is a decoupling of the execution of a certain task from
implementation.
• Every module can focus on what it is designed for.
• Modules make no assumptions about what other systems do but rely on
their contracts.
• Replacing modules has no side effect on other modules.

11. What is Dependency Injection (DI)?
• DI is a software design pattern that allows a choice of component to be
made at run-time rather than compile time.
• The binding of objects in the IoC pattern is accomplished through DI.
• Dependency injection involves at least three elements:
• A dependent consumer,
• A declaration of a component's dependencies, defined as interface
contracts,
• An injector (usually referred to as a container) that creates instances of
classes that implement a given dependency interface on request.

12. Why use IoC and DI?
• Encourages Separation of Concerns
• Facilitates unit testing by allowing mock object with known behaviors to be
injected
• Promotes loose coupling between application layers, allowing
implementations to be changed as necessary (i.e. mocks to SQL Server to
Oracle)

13. .NET Dependency Injection Frameworks
• Unity DI Container: http://unity.codeplex.com/
• Ninject: http://www.ninject.org/
• StructureMap: http://docs.structuremap.net/
• Spring.NET: http://www.springframework.net/

14. Microsoft Unity DI Container
Why Unity?

15. What is Unity and Why Use It?
• The Unity Application Block (Unity) is a lightweight extensible dependency
injection container
• Unity is developed and maintained by the Microsoft Patterns and Practices
team
• Unity is fully configurable using standard .NET config file patterns or through
code initialization

16. Recommended Tool Links
• Entity Framework: http://msdn.microsoft.com/data/ef
• Unity DI Container: http://unity.codeplex.com/

17. Questions and Discussion